Server-based call processing and call control is well known for the provision of packet-switched and Internet-based telephony and other call-oriented services. Conventional systems utilize call interfaces which are capable of managing packet-based or IP-based voice and data communications over the Internet, local area networks and wireless networks. These systems typically enable IP telephony through implementation of a call processing server having call processing hardware and software operative for call initiation and management of communications between endpoints using well known networking protocols, such as Transmission Control Protocol/Internet Protocol (TCP/IP), Real-time Transport Protocol (RTP), Session Description Protocol (SDP) and Session Initiation Protocol (SIP), etc.
As the need for network inter-working becomes more widespread, especially with the deployment of IP networks, there is an increasing need for service providers to interconnect with other networks that are using different signaling protocols. Thus, systems have been developed for implementing wireless telecommunication in packet-based networks. Examples of such systems are set forth in U.S. Pat. Nos. 7,200,139 and 6,671,364 and United States Patent Application Publication Nos. US 2008/0002673 and US 2006/0019655.
Half-duplex two-way radio systems are also well known, and offer certain advantages over conventional full-duplex wired and wireless communication systems. For example, two-way half-duplex radio systems provide immediate connection (i.e. the user merely pushes a button to talk, and is not required to dial a number and wait for a connection), automatic broadcasting to a group of radio endpoints on a common frequency (i.e. no need to establish a conference call), continued operation during natural disasters, snowstorms, etc., and are usually built to military standards capable of withstanding harsh operating environments and rough handling.
However, half-duplex radio systems also have certain limitations over conventional full-duplex communication systems. For example, in half-duplex communication mode (often referred to as push-to-talk (PTT)) a button is pushed when transmitting/talking and the same button is released when receiving/listening. That is, after the user of such a two-way radio depresses the “talk” button, other radio users tuned to the same frequency are prevented from transmitting/talking until the user releases the button. Thus, in contrast with full-duplex communication mode devices, a half-duplex radio cannot transmit and receive at the same time.
Accordingly, there exists a need to extend Internet-based telephony and other call-oriented services to half-duplex radio systems using existing network communication protocols, for integration with existing IP PBX networks as well as next-generation digital communication systems.
Similar reference numerals may have been used in different figures to denote similar components.